There are two types of electric charges: positive and negative.
If you play around with a magnet, you'll discover that the ends of the
magnet are the most powerful. One end is called the North Pole and the
other is the South Pole. Real simple to remember! Just think of Santa
Claus and elves! Each pole has a different type of charge, one is positive
and the other is negative. 
So, if you put two negative poles together, they push apart.
Likewise, if you put two positive poles together, they push apart.
If they're the same, they won't go together. But if they're different...
They pull together!
Just remember...Opposites attract, similar charges push back!